I might have a different perspective on this that may well not match your reality.
Imagine if you will that your husband is setting off on a journey. You have been his life-partner all along. He's lost and confused and doesn't "really" know what he wants and where he's going. While he's told you with his words that "he feels empty" he is still reaching out to you in many ways.
He says he wants to "be in love", he's searching for fulfillment. It may be that you could join him on this journey. If you read the books, they refer to something called "doing a 180" which means taking a look at what doesn't seem to work in your relationship and changing those things. Do you have any thoughts on what you might be able to consider to be a companion on his journey?
On the other hand, if he doesn't want you on this journey with him, that's a whole other set of issues. But from what you wrote in your initial post, I'm not completely sure that's the case.
Get and read the books but keep them to yourself. People going through transition don't want to be told that you're trying to "fix" them. Think deep and hard and honestly about yourself and your marriage. Both the good and the bad.
And keep posting. The more we know about you and your story the more we can try to help. We're mostly people struggling ourselves and we don't have all the answers, heck sometimes I'm pretty sure I don't even know the questions but it's a caring community that wants to help.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells